Summary Aim. The purpose of the study was to examine the relation between cognitive functioning in people with borderline personality disorder and their overall functioning level, as well as psychopathology intensification specific for this type of disorders. Method. 64 patients aged 18–55 (M = 30.09) with borderline personality disorder (emotionally unstable personality – borderline type in the ICD-10) were examined. The study used: demographic-descriptive questionnaire, SCID II, Borderline Symptom Checlist-23, and Global Assessment of Functioning (GAF). For cognitive assessment, The Rey Auditory Verbal Learning Test, The Rey–Osterrieth Complex Figure test, TMT A, TMT B, verbal fluency test, Stroop test and Frontal Assessment Battery (FAB) were used. Results. The average GAF score in the sample was M = 43.65. Significant differences between the comorbidity group and non-comorbidity group were observed with respect to the GAF scores (Mann-Whitney U = 300.500, p = 0.008) as well as a number of significant (p < 0.05) correlations between the level of cognitive functions and functioning in patients with no co-morbidity. Conclusions. Clinically significant disturbances in general and social functioning persisted in the group of subjects with borderline personality disorder. The obtained data seem to suggest that the cognitive functions affect the overall functioning only in patients with psychiatric co-morbidity. In people without psychiatric co-morbidity there is a relationship of cognitive functions only with certain aspects of psychopathology specific to BPD.